The invention relates to filter masks which isolate both the mouth and nostrils of a wearer from the surrounding environment. More particularly, the invention relates to a filter mask which provides a positive facial lock while requiring only a headband to secure the filter mask to the wearer's head.
There are many situations today where it is necessary to filter the air which is inhaled and exhaled. Such filtration is primarily concerned with removal of small particulate matter, such as dirt or bacteria, as opposed to gases or liquids, from the air. Perhaps the most common instance in which a filter mask is used is in the medical arts. However, the same filter masks which have application in the medical arts are also, in many cases, well suited for use in industrial and domestic applications as well.
In the medical arts, filter masks are often used to prevent nasopharyngeal organisms and materials which are exhaled by the wearer from entering the surrounding environment. The same mask may also be used to protect the wearer from inhaling harmful microorganisms. In both applications, it is important that the filter mask be fabricated from a material which exhibits a high bacterial filtration efficiency (BFE) and also have a structure that prevents the migration of microorganisms across the filter medium. One of the more common applications of filter masks in the medical arts is the wearing of masks by a surgical team while performing surgical procedures. A mask worn during surgical procedures, for example, must provide proper BFE while still being comfortable for the wearer who may be wearing the same mask for several hours.
In the industrial arts it is often necessary for individuals working in “clean room” environments to avoid the introduction of any particulate manner, including microorganisms which may be exhaled by the wearer, into the clean room environment. Some clean room environments may be significantly more “clean” (i.e., particle free) than the required level of cleanliness in some surgical operating room environments. Such clean rooms are required when fabricating what are termed very large scale integrated circuits (VLSIC) which are at the heart of modern electronic computers. As in the medical arts applications, industrial applications may require the workers to wear their filter masks for extended periods of time. Therefore, considerations of comfort and durability are of prime importance.
Other industrial applications require the filtration of the air which is inhaled by the wearer. Often construction or agricultural workers will be working in a “dirty” environment in which the air would be harmful to breathe if it were not filtered. Many times filter masks are used in such circumstances to protect the wearer from harm.
Besides the medical and industrial applications there are domestic applications for such masks in the home. Many hobbyists have uses for an efficient and comfortable filter mask. For example, an individual applying paint by means of a spray gun desires to ensure that the airborne droplets of paint are not inhaled. While filter masks may have application in a wide variety of fields, as exemplified in the prior discussion, it can be seen that the design requirements of filter masks to be used in these different applications share many common design criteria such as proper filtration, comfort and durability.
Regardless of te application, there are several considerations which must be raised when designing a filter mask to be worn by a human. First, the material used as the filter material must have the characteristic of preventing the passage of the size of particles which are desired to be filtered. The size of particles may vary between 10 micro-millimeters or smaller in the case of a bacterium, to a millimeter or more in the case of particles of dirt and dust. Furthermore, while still maintaining proper filtration efficiency, the filter material must allow for the passage of air without undue resistance. Also, the full benefits of the filter mask will not be realized if inhaled or exhaled air is allowed to leak around the edges of the filter material where the mask is not held securely against the wearer's face. Thus, if a positive facial lock is not maintained, the purpose of the mask may be defeated and the mask could be of little use.
Furthermore, the mask must be economical since most users of filter masks dispose of the mask after a single use. Still further, some applications may require that masks be changed regularly, for example every few hours when the wearer is working at an extremely dusty construction site. This consideration requires that both the materials used to construct the mask, and the method used to fabricate the mask, be such that costs are kept low. Furthermore, it is generally very desirable to design a mask which may be stored in a very small space. Generally, a flat storage configuration provides for the most compact storage.
Of immediate concern to the wearer of the mask is the comfort of the mask while it is on the wearer's face. Generally, the mask will be most comfortable if contact with the mouth is avoided. If the filter material contacts the wearer's mouth, the comfort, and often the integrity, of the mask is generally reduced. Furthermore, as various liquids from the wearer's face collect, such as perspiration and saliva, the portions of the mask held against the face may become saturated with liquid, thus reducing the comfort of the mask as well as presenting the potential risk of transferring microorganisms from one side of the filter material to the other. Still further, a filter mask should be relatively quick and easy to install, that is to place on the face, and should remain in the proper position while the wearer continues his ordinary activities.
In the prior art, many attempts were made to achieve some or all of these desirable characteristics in a filter mask. For example, U.S. Pat. No. 3,971,369 discloses a surgical face mask in which the filter material is folded so as to form a cup shape to prevent the filter material from resting against the face of the wearer. Still further, U.S. Pat. No. 4,300,549 discloses a filter mask which is provided with both pleats in the filter material and conformable stiffening members which are embedded within the filter material so that the filter material is held away from the wearer's face. U.S. Pat. No. 2,752,916 discloses a face mask which is held on the head by the use of a single headband which increases the ease with which the mask is placed on the wearer's face. None of these masks, however, addressed the problem of excessive “leaking” of air around the edges of the filter material, a common problem with nearly all masks available in the prior art.
U.S. Pat. No. 4,688,566 disclosed a mask which sought to solve this problem. The mask of the '566 patent has upper and lower edges which are provided with moldable stiffeners for conforming to the shape of the wearer's nose and cheek area and the lower jaw and chin area, respectively. The lower edge is folded so as to form a reverse pleat which conforms to the shape of the lower jaw. A single headband may be used to hold the mask on the head. The peripheral edges of the mask are bound. While the reverse pleat was good if only one headband was to be used, but it did not allow for the best fit possible on some face sizes and shapes. The reverse pleat uses up materials that could be used to obtain a better fit.
Thus, there is a need for a mask which overcomes the foregoing problems, but which also provides for a better fit on a wider range of facial sizes and shapes. The present invention provides such a mask.